Getting Fewer Hours Isn't The Biggest Sleep Change At Midlife & Here's What Is
Most women going through perimenopause expect their sleep to get worse. What they don't always expect is how it gets worse. It's not necessarily that you're sleeping fewer hours; it's that the sleep you're getting keeps getting interrupted.
A new large-scale study analyzing millions of nights of wearable data puts real numbers to that experience.
About the study
The SONAR study analyzed roughly 3.8 million nights of Samsung Galaxy Smartwatch data from 192,500 women aged 20 to 65 across the US, South Korea, Germany, France, and the UK.
Researchers tracked total sleep period, total sleep time, and wakefulness after sleep onset (WASO), meaning how long women stayed awake after initially falling asleep.
A parallel analysis was run on men in the same age ranges for comparison.
The real midlife sleep shift isn't about hours
The study's main finding was a notable jump in WASO starting at midlife. Women aged 50 to 54 were waking up 15% more than women in their early twenties. By ages 55 to 59, that gap widened to 25%, and for women aged 60 to 64, it reached 32%.
Meanwhile, total sleep time barely changed. Women in those same age groups were getting only about 17 minutes less sleep per night than the youngest group. So it wasn't that women were sleeping significantly less. They were just sleeping less continuously.
Men followed a similar trend, but the increases were smaller at every age. WASO rose by 9% for men aged 50 to 54, 16% for those aged 55 to 59, and 27% for those aged 60 to 64.
Why waking up matters more than you might think
Most conversations about sleep focus on hours: are you getting seven? Eight? But the SONAR data reframes the midlife sleep story around a different question: how often are you waking up, and how long are you staying awake once you do?
Fragmented sleep prevents you from reaching and sustaining the deeper, more restorative stages of sleep your body needs.
Those deeper stages are where the body focuses on healing and repair, and missing them repeatedly takes a real toll on your health.
Research links chronic sleep fragmentation to increased blood pressure, disrupted glucose metabolism, elevated stress hormones, and systemic inflammation, all of which raise the risk of cardiovascular disease and type 2 diabetes over time.
The hormonal connection
The main culprit is shifting hormones. As estrogen drops during perimenopause, your body loses some of its ability to regulate temperature, which is what triggers hot flashes and night sweats.
Those temperature spikes wake you up, and research suggests that waking up can itself trigger a hot flash, creating a cycle that's tough to break.
Falling progesterone adds to this: it's a naturally calming hormone that supports sleep, so when levels dip, sleep becomes lighter and more easily disrupted.
Mood is part of the picture too. Fluctuating hormones affect the brain chemicals that regulate anxiety, and poor sleep and low mood tend to feed each other.
How to support better sleep continuity
There are concrete, evidence-backed strategies that specifically target sleep fragmentation:
- Keep a consistent sleep schedule: Going to bed and waking up at the same time every day supports your body's internal clock and makes it easier to stay asleep through the night.
- Cool your bedroom down: Keeping your sleeping environment cool can help reduce the impact of hot flashes; layering bedding so you can adjust quickly without fully waking up can help you fall back asleep faster.
- Build a wind-down routine: Calming activities before bed (reading, a warm bath, meditation) signal to your body that it's time to sleep; limiting screens is worth prioritizing here, since the light they emit can suppress melatonin production.
- Move your body regularly: Weight-bearing and aerobic exercise support sleep quality, mood, and overall health during the menopausal transition; just avoid vigorous workouts too close to bedtime.
- Watch alcohol and late-day caffeine: Even small amounts of alcohol make it harder to stay asleep; excess fluids and caffeine in the hours before bed can also increase nighttime awakenings.
For women whose sleep disruption is more persistent, cognitive behavioral therapy for insomnia (CBT-I) is the frontline, non-medication treatment for insomnia and is specifically recommended for women navigating menopausal sleep changes.
When to bring it up with your doctor
Frequent nighttime awakenings during perimenopause and menopause are common, but they're not something you have to just accept. Many women don't seek treatment, often because the problem gets written off as a normal part of aging.
Insomnia (difficulty falling or staying asleep) and sleep apnea (brief awakenings, snoring, or non-refreshing sleep) are two different conditions with different treatments, and knowing which one you're dealing with matters for getting the right help.
The takeaway
Wwaking up more often at midlife is a pattern, not a personal failing, and it's one that responds to treatment. Knowing whether you're dealing with insomnia, sleep apnea, or hormone-driven disruption is the first step toward actually sleeping through the night again.
